The invention relates to a method for treating a drilling fluid and, more particularly, to a method for adjusting fluid density of a drilling fluid in a recoverable manner.
Drilling fluids are widely used in the petroleum industry during the drilling of wells to subterranean formations for production of hydrocarbons.
Drilling fluids are used for a number of purposes, including lubricating the drill bit, lifting rock cuttings to the surface and imparting a positive pressure against exposed formations so as to avoid influx of formation fluids into the well. The fluid density is directly related to the function of the fluid in imparting such positive pressure, as the density is the controlling factor in determining the weight of the drilling fluid column and the resulting hydrostatic pressure against the formation exposed by the well.
As different formations are encountered, and depth increases, drilling fluid density must frequently be adjusted to appropriately balance the system. Drilling fluid densities are typically adjusted from values between about 8.5 lb/gal (water) and about 15 lb/gal, and various powders and other additives are used for adjusting the density.
As fluid densities must be adjusted, drilling fluid must be adjusted by the addition of weighting material, repeated processes which can lead to a substantial amount of fluid and solid waste material. Of course, this is environmentally undesirable.
Further, such additions of additives take time and can result in significant delay before a new condition can be responded to with a change in density.
It is clear that the need remains for an improved method of adjusting drilling fluid density.
It is therefore the primary object of the present invention to provide a method for treating a drilling fluid which does not generate substantial amounts of solid and fluid waste material.
It is a further object of the present invention to provide such a method which is effective to produce a desired density change in a relatively short period of time whereby changing conditions can be rapidly responded to.
Other objects and advantages of the present invention will appear hereinbelow.
In accordance with the present invention, the foregoing objects and advantages have been readily attained.
According to the invention, a method is provided for treating a drilling fluid, which method comprises the steps of providing a drilling fluid; providing a drilling fluid additive comprising superparamagnetic nanoparticles; mixing said drilling fluid additive with said drilling fluid so as to provide a treated drilling fluid; and exposing said treated drilling fluid to a magnetic field so as to recover said superparamagnetic nanoparticles.
In accordance with a preferred aspect of the present invention, the fluid characteristic being adjusted is fluid density, and the superparamagnetic nanoparticles are substantially recovered for re-use in treating subsequent fluids.